Current perception threshold and reaction time in the assessment of sensory peripheral nerve fibers through sinusoidal electrical stimulation at different frequencies

Abstract

Introduction: The Perception Sensory Threshold (ST) for sinusoidal current stimuli at 5, 250, and 2,000 Hz is commonly used in the assessment of peripheral nerve fibers (C, Aδ, and Aβ, respectively

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“…Responses due to felt sensations in each block were categorized as suggested by Martins et al [14], in which blocks that contained words related to both groups (thin and thick fibers) are called BOTH, related to thin fibers THIN, and to thick fibers THICK. Thus, evaluation of perceived sensations -and indirect fiber activation -was performed by each group's percent change due to stimulus intensity increase.…”

“…The ST was evaluated through the current source Neurostim equipment [13,14]. Electrodes used for electrical stimulation were gold planar concentric (anode as a rim of 9-7 mm diameter and cathode as a 2 mm disc), suggested to have better specificity for Aβ-fiber stimulation, due to its increased focality and relative deepened electrical current density [16,22].…”

Cortical Alpha Oscillation During 3 kHz Steady-State Sinusoidal Electric Current Stimulation

“…During the past two decades, studies have shown that selectively activating Aβ-fibers ought to be attainable by using sinusoidal electrical stimulation of high frequencies, such as 2 kHz and 3 kHz, at the sensory threshold (ST) level as a psychophysical evaluation [13][14][15][16][17]. This is usually assessed through subjective questionnaire answers, where participants have to decide on words from a given list, that describe best the sensations felt after stimulation.…”

“…This is usually assessed through subjective questionnaire answers, where participants have to decide on words from a given list, that describe best the sensations felt after stimulation. Thus, it is a forced-choice paradigm that highly depends on individual's cognitive state, and whether this type of stimuli elicits conscious tactile-related responses cortically was not yet assessed [9,13,14,16].…”

“…Electric pulse stimulus has also been extensively used with this purpose, [9] and although it has been reported that it seems to evoke tactile perception artificially in a given intensity [9], it is known that it provides recruitment of thick fibers firstly (Aβ) and thin fibers in a second moment (Aδ and C), especially with increasing stimulus intensities [10,11]. Selectively activating Aβ-fibers could be rather useful for disease evaluation -i.e., diagnosis and progression of conditions that involve sensorial and tactile loss, such as stroke, diabetes mellitus, phantom limb pain and leprosy [12][13][14][15][16].…”